The present invention relates generally to a mounting device for a firearm, and is particularly concerned with a mounting device for mounting an accessory such as an optical sight on a firearm.
There are many different types of optical sights or telescopic sights for mounting on firearms such as rifles. Such devices are typically secured to a rail or adapter, which in turn is secured to the rifle itself. One well known adapter for mounting certain types of optical scopes or sights on a rifle is the so-called “Picatinney” rail, which is a straight rail having spaced lugs extending along opposite sides of the rail, with a gripping chamfer on the outer face of each row of lugs. This is designed to engage with a corresponding channel on the base of the optical scope or sight. The Picatinney rail will work with most optical sights currently available. A Picatinney type of mounting rail is described in U.S. Pat. No. 6,381,895 of Keeney et al. and U.S. Pat. No. 6,449,893 of Spinner, for example.
Another well known optical sight is the ACOG® or Advanced Combat Optical Gunsight made by Trijicon Inc. of Wixam, Mich. This gunsight cannot be mounted directly on a Picatinney rail since it has a different mounting assembly of a lug designed to engage in a channel. The current mounting solution is to mount an adapter on top of a Picatinney rail to accommodated the ACOG® optical sight. One problem with this arrangement is that use of an adapter on top of the mounting rail raises the height of the optical sight above the center bore of the rifle to an unacceptable level, requiring the shooter to raise their head unnaturally to obtain a sight picture. This will reduce shooting accuracy. Also, the adapter creates a weak link in the assembly which adds further attachment points which could loosen. It is important for accuracy that the optical sight remains rigidly attached to the rifle.
Another problem inherent in previous mounting rails and adapters for mounting optical sights on rifles is that the optics are typically positioned too far forward, at a distance exceeding the required eye relief range of one to three inches from the shooter's eye to the sight. This causes the shooter to try to crane his or her head forward to distance themselves at the appropriate spacing from the ocular end of the sight.